Power semiconductor modules have electrical connecting contacts for the electrical connection of module-external components, the contacts being accessible from the exterior of the module and being electrically conductively connected to one or more power semiconductor chips or other components arranged in the interior of the module. In this case, the electrical connection is at least partly realized by low-resistance electrical conductors, referred to hereinafter as connecting lugs. Such connecting lugs have to be connected to the housing in a sufficiently stable manner in order to prevent a module-external mechanical loading of the connecting contacts from being transmitted to other, module-internal components via the connecting lugs in an impermissible manner.
In order to avoid this problem, the connecting lugs in principle can be provided for a specific module layout and encapsulated by injection molding during the production of a plastic injection-molded housing for the power semiconductor module. However, this has the disadvantage that a dedicated injection mold is required in each case for different module layouts.
In order to electrically connect a connecting lug internal to the module, bonding connections can be used or also soldering, welding or electrically conductive adhesive connections. Switching currents for such modules tend to increase as a result of technical advancements. As such, bonding wires composed of copper or a copper alloy are increasingly being used instead of customary aluminum bonding wires. In comparison with aluminum bonding wires, however, copper-based bonding wires are significantly harder, for which reason the press-on force exerted on the bonding wire during the bonding process has to be significantly higher in the case of a copper-based bonding wire than in the case of an aluminum bonding wire. However, this has the effect that more stringent requirements have to be made of the mechanical connection between a connecting lug and a housing element of a power semiconductor module since the press-on force loads the mechanical connection between the connecting lug and the housing element.
Also of concern is the accuracy of the positioning of the connecting lugs. This is important firstly for module-internal electrical connections, for example if bonding wires are intended to be bonded to the connecting lugs in the interior of the power semiconductor module. Secondly, in the case of modules having a housing cover, it may be necessary to place the housing cover onto the connecting lugs in an accurately fitting manner. Moreover, the module-external connecting contacts of the connecting lugs have to be electrically connected to other components. Depending on the configuration of the other components, this may require a precise alignment of the connecting contacts and hence of the connecting lugs. As such, the connecting lugs are conventionally realigned after the mounting process in a separate step which increases cost and reduces yield.